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(July 24, 2009). doi:10.1510/mmcts.2006.002378 Copyright © 2009 European Association for Cardio-thoracic Surgery Procedure Surgical management of hypoplastic left heart syndrome at the Birmingham Children's HospitalBirmingham Children's Hospital, Cardiac Surgery, Birmingham, B4 6NH, UK * Corresponding author: Tel.: +44-121-333 9435. almafa{at}web.de
Currently, a three-stage surgical palliation remains the treatment of choice at Birmingham Children's Hospital. After initial introduction of the classical Norwood with pulmonary blood flow provided by a modified Blalock–Taussig shunt, a right ventricular to right pulmonary artery conduit at stage 1 Norwood palliation is now used in most cases, a bi-directional ‘Glenn’ shunt at second stage and an extra-cardiac Fontan completion at third stage. Mortality and morbidity has improved after modification of the technique. Thirty-day mortality was 32.4% (79/244) for the ‘classical’ Norwood procedure, 25.0% (7/28) for the left-sided RV-PA conduit and 12.7% (22/173) for the right-sided RV-PA conduit. Interstage mortality was 8.6% (21/244) for the ‘classical’ Norwood procedure, 14.3% (4/28) for the left and 10.1% (15/148) for right-sided RV-PA conduit. After stage II, 30-day mortality was 3.0% (10/335) for all groups. Stage III 30-day mortality was 0.9% (1/115) for all groups.
Key Words: CP shunt • Fontan procedure • Hypoplastic left heart syndrome (HLHS) • Left ventricular hypoplasia • Norwood procedure
The term hypoplastic left heart syndrome (HLHS) was introduced by Noonan and Nadas in 1958 [1]. Its prevalence is about 0.16–0.26 of 1000 live births of neonates in whom heart disease is diagnosed in the first year of life [2]. Without surgical intervention, HLHS is fatal and can account for 25% of cardiac deaths in the first week of life.
Morphology The right ventricle supports the systemic circulation via a persistant ductus arteriosus PDA. The left atrium tends to be smaller than normal and there is typically retrograde flow in the ascending aorta to the coronary arteries. Rarely, there is a restrictive foramen ovale or completely closed atrial septum. In the past, the diagnosis was made postnatally but currently in 40–85% [6] of cases HLHS is diagnosed antenatally between 18 and 22 weeks of gestation [7].
Pathophysiology
Management
The three-stage surgical approach in Norwood procedure for palliation of hypoplastic left heart syndrome
Stage I: Norwood procedure The first stage palliation establishes unobstructed systemic and coronary blood flow from the right ventricle, unobstructed pulmonary venous return across the atrial septum and a balanced flow between the systemic and pulmonary circulations. The components of the first stage palliation consist of (a) anastomosis of the proximal pulmonary trunk to the aorta with homograft augmentation of the aortic arch, (b) atrial septectomy, and (c) establishment of a systemic to pulmonary shunt. The procedure was first described by William Norwood, who originally used a Blalock–Taussig shunt for blood supply to the pulmonary arteries ([11, 12] Schematic 1A). The procedure has since undergone a variety of modifications in terms of arch reconstruction and modification of blood supply for the pulmonary arteries. The latest modification consists of a right ventricular to pulmonary artery shunt introduced by Sano et al. [13] with the advantage of higher diastolic pressures to aid perfusion of coronary arteries. The RV-PA conduit has become an increasingly popular technique, taking the conduit to the left of the neo-aorta. At Birmingham Children's Hospital, we have modified the RV-PA conduit to route it to the right side of the neo-aorta.
The patient is in a supine position; a central venous line is placed in the groin and an arterial line is placed preferentially in the right radial or brachial artery. The surgical approach is through a median sternotomy: the thymus is excised subtotally, the great vessels, their branches and the duct are all dissected free (Video 1), mobilized and encircled with silk ligatures, followed by heparinization.
Arterial cannulation is effected by direct cannulation of the ascending aorta, if the aorta is of adequate size. Alternatively, if the aorta is <4 mm in diameter, the innominate artery is used for arterial access: the artery is dissected free superior to the innominate vein (Video 2), a side biting clamp placed and a 3-mm thin walled Gore-tex® tube [WL Gore & Associates (UK) Ltd., Livingston, Scotland] anastomosed using 8-0 Prolene (Video 3).
An arterial line is advanced and secured within this tube. In case of a normal sized aorta, the latter may be cannulated directly and the tip of the cannula later advanced into the brachiocepahlic artery for antegrade cerebral perfusion during arch reconstruction. A single venous cannula is placed in the right atrial appendage, establishing cardiopulmonary bypass. Immediately after commencing bypass, the duct is ligated and the patient gradually cooled down to 18 °C at full flow. During cooling, and while the heart is still beating, the proximal pulmonary trunk is divided above the commissures of the pulmonary valve, leaving a vascular clamp on the proximal pulmonary trunk (Video 4).
The defect in the distal trunk proximal to the junction of the branch pulmonary arteries is either closed directly using a 7-0 prolene suture (Video 5) or, if the opening is close to the branch pulmonary arteries, a piece of thin walled Gore-tex® conduit may be used to patch this area.
A thin walled Gore-tex® conduit is used for the right ventricular to pulmonary artery (RV-PA) conduit and is anastomosed to the anterior aspect of the right pulmonary artery (Schematic 1C, Video 6).
A 5-mm conduit is used for neonates  2.5 kg and a 4-mm conduit is used for neonates <2.5 kg. A short diagonal incision is made in the infundibulum of the right ventricle inferior to the pulmonary artery and the edges are undermined to create an unobstructed outflow. The Gore-tex® conduit is tailored in length and anastomosed to the incision, using 7-0 prolene (Video 7). This can be done on the beating heart if the aorta is atretic, otherwise the aorta is cross-clamped and cardioplegia given prior to this step to avoid any risk of air embolism. Having completed the anastomosis of the proximal RV-PA conduit, the circulation is arrested: all head vessels are occluded except the brachiocephalic artery which is occluded distal to the arterial line by snugging down the previously placed silk snares. A clamp is placed on the descending aorta distal to the coarctation ridge and the heart is arrested with cold crystalloid cardioplegia given through the side arm of the arterial cannula (30 ml/kg). The brachiocephalic artery is then snugged down, proximal to the arterial cannulation site.
The atrial cannula is removed and an atrial septectomy performed through the atrial cannulation site (Video 8). The atrial cannula is then placed back into the appendage of the right atrium and antegrade cerebral perfusion can be instituted at this point via the brachiocephalic artery at half flow (8 ml/kg/min).
The duct is then divided at its junction with the descending aorta, the descending aorta further mobilized, preserving the recurrent laryngeal nerve, and all ductal tissue at the aorta excised (Video 9). The incision is extended distally into the descending aorta and proximally along the concavity of the aortic arch into the ascending aorta down below the level of the transected pulmonary arteries and into the aortic root (Video 10).
If a prominent coarctation ridge is present this is resected and the posterior wall is reconstructed with 7-0 prolene (Video 11). However, if there is only a mild or no ridge then no resection is performed.
The arch is then reconstructed with a patch of pulmonary homograft using continuous 7-0 prolene (Video 12). Before completion of this anastomosis, a separate incision is made into the homograft patch to receive the main pulmonary artery which is then anastomosed into this opening (Video 13) and the neoaortic reconstruction is completed (Video 14).
After full rewarming the patient is weaned off bypass on Milrinone 0.5 µg/kg/min and adrenaline 0.05–0.2 µg/kg/min to maintain a mean blood pressure of 40–45 mmHg and a target arterial oxygen saturation of 70–80%. An on-table epicardial echocardiogram is used routinely to assess RV function, tricuspid valve regurgitation, RV-PA conduit flow, the atrial septectomy, and flow through the aortic arch. The chest is routinely left open with a chest drain and a peritoneal drain being placed and a fenestrated soft-tissue Gore-tex® patch is placed between the skin edges. The patient is transferred to the intensive care unit and remains fully paralyzed and sedated until the sternum is formally closed depending on haemodynamic stability after 48 h postoperatively; target arterial oxygen saturations are 70–80%, mean blood pressure 40–45 mmHg and mixed venous saturations are used to optimize cardiac output aiming for an arterio-venous difference of <30% [16]. Heparin is started within 12 h postoperatively with a rate of 10 IU/kg/h.
Stage II: superior cavopulmonary connection Stage II is performed at 4–6 months of age. In view of the relatively young age and the importance of obtaining optimal access to the pulmonary arteries we prefer to perform the stage II anastomosis under a period of deep hypothermic circulatory arrest. To perform a superior cavopulmonary connection, deep hypothermic cardiopulmonary bypass is established between the neoaortic arch and right atrium. The Gore-tex® shunt is divided between ligatures and the distal end excised. The proximal end is oversewn and left in situ. A stenosis of the pulmonary artery secondary to the prior shunt or patch is repaired using a patch of pulmonary homograft. The azygous vein is ligated. The SVC is divided at its junction with the right atrium and oversewn with 5-0 prolene, taking care to avoid the sinus node (Video 15). The SVC is anastomosed end-to-side to the superior aspect of the right pulmonary artery using continuous 6-0 polydioxane (PDS) sutures (Video 16). Thus, the calibre of the SVC, rather than the calibre of the right pulmonary artery defines the size of the anastomosis.
Stage III: total cavopulmonary connection (TCPC) Patients are assessed by cardiac catheterization approximately 24–36 months after the stage II procedure and the patient is managed similarly to any other patient going down the single ventricle pathway.
Our policy is not to have a fixed age for completing the Fontan circulation. Rather, the decision is based on findings at catheter and primarily, on clinical symptoms and degree of desaturation. This is generally at an age of 4–6 years. Significant narrowing of the branch pulmonary arteries – most commonly a degree of tubular hypoplasia of the left pulmonary artery – is treated with uncovered stent placement or with surgical patch reconstruction prior to stage III. Patients with a pulmonary artery pressure
The HLHS programme at Birmingham Children's Hospital begun in 1992 as the first in the UK. From October 1992 to December 2007, 445 patients presenting with true hypoplastic left heart syndrome or variants of that diagnosis underwent the Norwood stage I procedure; of these, 244 patients were treated with the ‘classical’ Norwood procedure (group A). From April 2002, 201 patients were treated with an RV-PA conduit modification. The RV-PA was initially to the left side (n=28, group B), as described by Sano et al. [13], but from October 2003, this was changed to our own modification of the right-sided conduit (n=173, group C) as described above. Thirty-day mortality was 32.4% (79/244) in group A, 25.0% (7/28) in group B and 12.7% (22/173) in group C. Median cardiopulmonary bypass time was 66 min for the classical Norwood, 105 min for the left-sided conduits and 115 min for the right-sided conduits. At the end of December 2007, 272 out of 445 patients had reached stage II, 25 patients were still in between stage I and II. The remaining 148 patients account for the interstage mortality in between stage I and stage II, which was 8.6% (21/244) for group A, 14.3% (4/28) for group B and 10.1% (15/148) for group C, thus, demonstrating a difference in techniques. Kaplan–Meier actuarial survival curves are shown in Graph 1.
After stage II, 30-day mortality was 3.0% (10/335) for all groups, and 5.5% (8/145) in group A, 0% (0/76) in group B and 1.7% (2/114) in group C; interstage mortality in between stage II and stage III was 16.5% (24/145) for group A, 0% (0/12) for group B and 5.2% (6/114) for group C, including early death (30 days). We have an aggressive approach to pulmonary artery reconstruction and treat any reduction in diameter of 25% with patch enlargement at time of stage II surgery. Consequently, the incidence of central pulmonary patching has been 48.9% (42/145) in group A, 88.2% (15/17) in group B and 60.5% (69/114) in group C. The change in technique to the right-sided RV-PA conduit was developed to improve access to the central pulmonary arteries at the time of stage II. This led to decreased reconstruction time intraoperatively: medium cardiopulmonary bypass time for reconstruction of central pulmonary arteries was 43 min for the classical Norwood, 60 min for the left-sided conduits and 49 min for the right-sided conduits. Stage III 30-day mortality was 0.9% (1/115) for all groups, and 1.0% (1/100) in group A, 0.0% (0/8) in group B and 0% (0/7) in group C and 1-year mortality after stage III was 5.1% (5/98) in group A, 0.0% (0/0) in group B and 0% (0/0) in group C (Table 1).
The Norwood procedure has revolutionized the management of HLHS and became one of the most challenging and dramatic developments in neonatal cardiac surgery over the past 25 years. The procedure has undergone a variety of developments and modifications over the years both in terms of surgical technique and in perioperative management and the outcomes have been characterized by a steady and remarkable improvement. Historically, a Blalock–Taussig shunt was the first choice of pulmonary blood flow as described by Norwood, and was later changed to a modified Blalock–Taussig shunt [10, 11]. However, there are disadvantages in using the modified Blalock–Taussig shunt with the Norwood procedure, because blood flows into the pulmonary arteries in both systole and diastole, thus, leading to a steal effect leading to inadequate pressure to supply the coronary arteries. The competing blood flow between the pulmonary and coronary arteries can result in sudden haemodynamic changes and instability after the operation. In 2003, Sano published his experience with a left RV-PA conduit which markedly improved hospital survival from 53% to 89% [13]. We reproduced these results in our institution [14]. The advantage of the Sano shunt as compared to the Blalock–Taussig shunt was the maintenance of a stable diastolic systemic pressure and no diastolic steal of coronary blood flow. That leads to improved early postoperative haemodynamics, however, it requires an incision on the right ventricle, with still unknown consequences concerning long-term ventricular function. This technique has been quickly adopted at other centres, many of whom have reported an improvement of outcome. However, it has by no means been adopted universally and many experienced proponents of the classical technique continue to publish excellent results [15]. Both techniques are being applied currently in different centres, with a gradual improvement of postoperative outcome in every technique over the last years. This may in part be explained by better understanding of the physiology and perioperative management following either one of the techniques. At our institution, the Birmingham Children's Hospital, we gained experience with both techniques over a study period of 10 years (1997–2007), and have clearly identified an improvement in outcome after staged surgical management of HLHS, which was primarily attributable to changes in surgical technique [16]. The RV-PA conduit, in particular, was associated with a notable and independent improvement in early and actuarial survival [14]. However, others have found no difference in hospital survival when comparing both techniques [17] in a non-randomized study. Sano originally described the anastomosis of the RV-PA shunt to the left pulmonary artery, but, the frequency and severity of central artery stenosis at the site of insertion in our patients led to our modification of the RV-PA conduit with anastomosis to the right pulmonary artery (Schematic 1C). We felt that mobilization of the left pulmonary artery as well as the neoaorta to access a stenosis seemed more complex and time consuming, while the right-sided RV-PA conduit offers the benefit of utilizing an anatomic site where the bidirectional Glenn shunt will be created later. Thus, our bypass and ischaemic times were reduced in patients that were treated with a right-sided shunt. Survival was better in patients with a right-sided shunt as compared with the left-sided shunt, although patients in both groups were similar in terms of preoperative patient characteristics, as well as operative time. Use of a right-sided RV-PA conduit as opposed to the left-sided conduit in this cohort did lower the overall incidence of pulmonary stenoses; however, narrowing at the site of the anastomosis seems to be a constant problem and may be inherent to this technique. Despite the problem of central pulmonary artery stenosis there is evidence that the RV-PA conduit provides better growth of distal pulmonary arteries compared with the modified Blalock–Taussig shunt [18, 19], which may be related to more pulsatile flow. The technique for repair of the coarctation we use was first described by Jonas et al. [20] based on the fact that most of the patients presented with coarctations that could not be dealt with by the technique originally described by Norwood, who created a neoaorta using the proximal pulmonary artery anastomosed to the ascending and proximal aortic arch [10]. We previously described a different technique, which was based on reconstruction of the neoaorta without patch supplementation [16]. However, this technique was more technically demanding, requiring several technical adjustments for each patient, and was abandoned in favour of the patch reconstruction described in this article. We believe that use of patch augmentation for the arch and ascending aorta, which we adopted in 1999, provides a more reproducible and easier surgical technique. Complete resection of the coarctation ridge leads to a higher rate of catheter based re-interventions, particularly on the left pulmonary artery [12]. This may be because the technique effectively lowers the height of the arch and reduces the volume of the concavity of the neoaortic arch, trapping the left pulmonary artery. Improved outcomes in the Fontan circulation in HLHS have been characterized by the adoption of a staged approach and the use of the cavopulmonary shunt as an interim stage prior to the TCPC. This reduces the volume load on the systemic circulation resulting in lower systemic venous pressures [21] without increasing pulmonary blood flow too dramatically at this early age while also allowing for any necessary reconstruction of the central pulmonary arteries. The second important technical development has been the use of a fenestration in the Fontan circuit [22, 23]. Arterial oxygen saturation is lower, but cardiac output is higher and may even reduce severity and duration of postoperative pleural effusion and length of hospital stay [24] – although has not been consistently seen in all series. However, this has not been confirmed in our patients. It is our clinical practice to advise life-long anticoagulation with warfarin to reduce the risk of paradoxical embolism, to reduce the possible thrombus formation in the external conduit, and to minimize micro-thrombus formation that may lead to chronic pulmonary embolic events with gradual increase of pulmonary vascular resistance. Over time there has been a significant improvement in outcome after reconstructive surgery due to refinements of surgical techniques and better understanding of perioperative physiology in HLHS. The three-stage Norwood procedure has become the mainstay for surgical management of HLHS.
First and foremost we would like to thank the parents and patients and second we express our thanks to our colleagues and staff in theatres, on the paediatric intensive care unit, as well as on the ward.
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Summary
Introduction
